Guwahati, Sep 29 (IANS) At least six people, including two paramilitary troopers, were critically injured Thursday in a powerful bomb explosion at a crowded market in Assam, officials said.

A police spokesman said militants suspected to be from the outlawed United Liberation Front of Asom (ULFA) triggered an improvised explosive device at the main market in the oil township of Digboi, about 530 km east of here. The incident took place about 7 p.m.

"Four shoppers and two soldiers of the Central Reserve Police Force were wounded in the blast. The market was totally packed with people when the explosion took place," Tinsukia district magistrate Absar Hazarika told IANS over phone.

"The ULFA is behind the attack," he said.

The injured were shifted to a local hospital with multiple injuries.

This is the latest in stepped up attacks by the ULFA that led the Indian government to call off a six-week old ceasefire Sunday and resume military operations against it.

The ULFA last weekend killed a policeman and a tea plantation manager in Tinsukia.

On Wednesday, a group of ULFA-appointed peace negotiators pulled out of the peace process, further dimming chances of direct talks between the rebels and Indian authorities.